Autunite specimen from China

Recently I’ve bought a little specimen of Autunite from China. My specimen is 20mm lenght, 15mm width and 6mm thick with nice green lamellar crystals. I’ve bought it from a chinese seller because I couldn’t find an equally nice sample from Europe.

Autunite specimen

I’ve received it after 30 days from the order. Immediately I’ve painted it with transparent acrylic pain to avoid contamination with tiny powder that could be lost by the speciment during handling.

I’ve tested it with my SV500 geiger counter that measure beta+gamma at contact in the range of 20-25mRad/h and 3-5mRad/h of gamma’s only. This is an highly active sample as expected. It’s radiation become inconsistent at just 10cm from the sample and just my scintillation probe could measure it. I’ve made a gamma spectrum of it’s emission with a NaI(Ti) scintillator.

Autunite gamma spectrum

As you can see it’s easy to detect it’s thorium and radium content. There are also decay products like Pb214. Bi214 is a characteristic decay product of Ra226. Take a look at the Ra226 decay chart below

Ra226 decay chart

In conclusion this specimen is not a fake made in China, is just a nice high activity sample.

NER10 X-Ray generator

I’ve bough from eBay a NER10 X-Ray generator tube. It was build in 1925-1930 I don’t know exactly when. It’s interesting to see how well made it is also, It’s massive and big in size and weight.

NER10 x-ray generation tube

I’ve no datasheet of this tube. Everything I know about this tube, I learned on this video

Der Floureszenzschirm befindet sich hinter dem Pappschirm.
Das Bild wird von dem quadratischen Spiegel (mit rotem Rand) wiedergegeben.
Diese Anordnung hat den Vorteil,daß die Kamera auf der nicht ganz so strahlenverseuchten Seite der Röhre stehen kann.
Die Röhre ist eine Phönix Radion Ner10,etwa 1925-1930 hergestellt.
Der Anodenstrom beträgt im Video etwa 3mA (bis 7mA sind möglich,allerdings geht dann die Spannung in die Knie) bei einer Spannung von etwa 50kV.
Der Heizstrom harmoniert am besten mit dem Hochspannungsteil (Röhrenwiderstand) bei etwa 2,8A.
Die Anodenspannung wird mit einem AC-Zeilentrafo,welcher von einer ZVS-Schaltung getrieben wird,und einer nachgeschalteten Kaskade erzeugt.
Die Kaskade ist in einem PVC-Rohr mit Ölfüllung untergebracht.Die Dioden der Kaskade vertragen einen Strom von 10mA@20kV;
die Kondensatoren haben eine Kapazität von 1nF und eine Spannungsfestigkeit von 15kV. 
Das ganze Teil sollte in einem Steampunk-Bakelit-Holz-1930er Jahre-Design rüberkommen.
Darum habe ich bewust diese alten Drehschalter verwendet.
Das obere Amperemeter zeigt den Röhrenstrom in mA an,das untere den Heizstrom in A

I don’t speek german but I think Google traducer made a good job:

The fluorescent screen is located behind the cardboard umbrella.
The image is reproduced by the square mirror (with red border). 
This arrangement has the advantage that the camera can stand on the not so sun-contaminated side of the tube.
The tube is a Phoenix Radion Ner10, made about 1925-1930.
The anode current in the video is about 3mA (up to 7mA are possible, but then the voltage goes to the knee) at a voltage of about 50kV.
--> IT NEED 50kV Nice!!!
The heating current harmonizes best with the high voltage part (tube resistance) at about 2.8A.
The anode voltage is generated with an AC line transformer driven by a ZVS circuit and a downstream cascade.
The cascade is housed in a PVC pipe with oil filling. The diodes of the cascade tolerate a current of 10mA @ 20kV;
the capacitors have a capacity of 1nF and a dielectric strength of 15kV.
The whole piece was supposed to come in a steampunk bakelite wood 1930s design.
That's why I've deliberately used these old rotary switches.
The upper ammeter indicates the tube current in mA, the lower the heating current in A.

This is the Anode, the corroded point is where electrons hits the metal and generates xray’s

The copper anode and the hole

The copper anode and the hole where the filament heats up.

Let we see the marks on the tube


The cathode socket with two wires soldered by me

Cathode socket

Anode is made of turned steel or maybe copper plated steel?

Radioactive sources

This is my actual collection of radioactive sources.

Thorium Kodak lens

Kodak had made some 35mm analog film models of cameras (1950-1970) like Retina IIIc, with thoriated lens. This example is a Retina-Xenon made with thoriated glass. It could be 30% by weight of thorium oxide

This is the gamma emission spectrum of the lens. Mine STS-6 geiger counter one centimeter in front of the lens count aprox. 180 CPM It emit mainly gamma’s and betas… but nothing dangerous for the photographer.

Thoriated welding rods (red for TIG)

Thoriated welding rods for TIG application is a very common and secure radioactive source. You could find the rods at local hardware store. Usualy they are 98% tungsten + 2% thorium by weight. Emission of gamma rays are low, barely over natural background. on the STS-6 geiger counter three rods add 20-30 CPM on the natural background. It mainly emit beta plus some little gamma.

Pechblende uranium ore from Novazza mine

This sample of pechblende is from the biggest mine of uranium in Italy. And in Italy mines are 2… maybe 3 🙂 lol! It come’s from Novazza. The STS-6 counts… 14-16000CPM!!! And SV500 with beta+gamma window opened is in the range of 10-12mRad/h. I store it into a lead enclosure with 5mm thik walls. It’s main emission is… everythink! There is a lot of alpha, A LOT of beta and some cool gamma.

Americium from ionization chamber

You can buy (1.5-2€) from china this little device: an ionization chamber!

It contain some uCurie of americium radioisotope wich emit alpha and some gamma ray. My SV500 placed with beta+gamma window opened fell it like a 1mRad/h source. The main emission of the americium sample is alpha rays but it emit some 59keV gamma rays too.


Please note that if handled correctly, objects manufacted with radioactive isotopes into methal alloy or paint are not dangerous, anyway there are some exception. Eating or breathing radioactive isotopes is dangerous. Don’t pulverize or eat radioactive ores or objects containing radioactive isotopes. Natural radioactive ores could be dangerous if their size are big (emission intensity grow with quantity of emitting material) and if their composition activity is high. Please consider testing natural ores with a calibrated geiger counter in order to ceck it’s activity (must be less than few milliRad/h). Store highly active material into lead shielded enclosures in a secure place.



MadEXP PMT Adapter v2.0 schematic/gerber files plus license. Click on the link to download.

MadExp PMT

MadEXP PMT Adapter v2.0 preview

MadEXP PMT Adapter v2.5 schematic/gerber files plus license. Click on the link to download. Added mounting holes.

MadExp PMT v2.5

MadEXP PMT Adapter v2.5 preview

Bill of material. This is the bill of material from Mouser. Please note that some component like the multiturn trimmer and the audio IC are missing. The trimmer was bought from a stock on eBay, same thing the IC CM108AH. The low leakage zener diode on the feedback circuit was bought from a german military surplus stock. Hard to find part, search on eBay.

Bill of material

Z80 Single Board Computer

This is my first didactic 8bit – Z80 based computer.

I’ve made it because I was interested into homebrew such type of computer since high-scool times but never do it. I was intrigued by the idea of better understanding of PC architecture and  I wish to learn programming with assembler language.

My project starts copying Grant Searle’s magnificent project: Grant’s 7 chip Z80 Computer Please note that I’ve changed the way of the UART/RS232 converter is wired. In fact I’ve lost a lot of time following Grant’s schematic: everything double cecked but no data received to the serial port… uhm… I’ve solved in this way:

No jumpers between DB9 connector pins or other RTS shit… just a simple straight RX-TX converter between 6850 UART and DB9 connector.

I’ve build it using point-to-point wire soldering on a veroboard prototyping board. At the moment it comunicate with me via a RS232 serial link.

The schematic is the same of the Searle’s website except I’ve modified the clock source and the init.asm code that drive the 68B50 ACIA.

I’m using a 1.8432Mhz crystal oscillator at first for cpu and ACIA then switched to drive the cpu via a 10.240Mhz crystal oscillator. The 1.8432Mhz crystall just drive the ACIA.

I’ve benchmarked it’s performance via the Mandelbrot generator provided by the RC2014 project.

color_mandelbrot    mandelbrot

This RC2014 project started years ago like mine copying the Searle’s project and improving it so it’s 100% compatible with mine.

The results? At 1.832Mhz it took 46:52 Minutes to complete. At 10.240Mhz just 8:31 minutes



MS-4 γ-selective Geiger counter

This is a γ-selective Geiger counter from the “M” professional serie used also in demonstration devices for measuring the age of minerals by the activity of the isotope potassium-40. It’s a classic all-glass construction with platinum cathode.

Tech. spec.:

·Radiation determine: (γ) gamma soft/hard
·Voltage of start of counting: 720 – 780V ;
·Operating voltage (recommended): 820 – 880V;
·Length of flat part of counting curve (plateau): 200 V
·Slope of the counting curve: < 0.1 %/V;
·Sens. background: < 65 counts/min;
·Maximum counting range: 5*10E4 counts/min
·Load resistance: 8 – 15 MOhm
·Counter resistance: 4 – 8 MOhm
·Allowable stray input capacitance: < 25 pF
·Working temperature range: -40…+50 C
·Anode material: Platinum (Pt)
·Cathode material: Copper (Cu)
·Weight: ~30g.
·Dimensions: counter length 175mm, diameter 21.5mm


This is equivalent to SBM20

Tech. spec.:

·Radiation determine: beta ( > 0.25 MeV) ; gamma soft/hard
·Voltage of start of counting: 280 – 330 V ;
·Operating voltage (recommended): 360 – 440 V;
·Length of flat part of counting curve (plateau): 80 V
·Slope of the counting curve: < 0.12 %/V;
·Natural background: < 0.4 counts/s;
·Maximum radiation: 1*10E5 counts/min;
·Load resistance: > 8 MOhm
·Allowable stray input capacitance: 10 pF
·Working temperature range: -50…+70 C
·Weight: ~10 g.
·Dimensions: counter length 110mm, max.diameter 12mm

AC-1 High-sens β-selective Geiger counter

This tube is very hard to find. It’s made from alluminium and glass and is a β-selective Geiger counter. It’s counts only beta’s!

Tech. spec.:

·Radiation determine: (β-) beta soft/hard
·Voltage of start of counting: 750 – 860V ;
·Operating voltage (recommended): 830 – 940V;
·Length of flat part of counting curve (plateau): 80 V
·Slope of the counting curve: < 0.2 %/V;
·Natural background: < 40 counts/min;
·Maximum radiation: 2*10E7 counts/min
·Load resistance: 50-80 MOhm
·Allowable stray input capacitance: < 25 pF
·Working temperature range: -0…+50 C
·Anode material: Platinum (Pt)
·Cathode material: Aluminium (Al)
·Weight: ~20g.
·Dimensions: counter length 128mm, diameter 17mm